Function apply_migrations

pub async fn apply_migrations(
    db: &Database,
    kind: String,
    target_db_version: DatabaseVersion,
    migrations: BTreeMap<DatabaseVersion, CoreMigrationFn>,
    module_instance_id: Option<ModuleInstanceId>,
    external_prefixes_above: Option<u8>,
) -> Result<(), Error>

apply_migrations iterates from the on disk database version for the module up to target_db_version and executes all of the migrations that exist in the migrations map. Each migration in migrations map updates the database to have the correct on-disk structures that the code is expecting. The entire migration process is atomic (i.e migration from 0->1 and 1->2 happen atomically). This function is called before the module is initialized and as long as the correct migrations are supplied in the migrations map, the module will be able to read and write from the database successfully.